Humanity gradually outgrew the need of these gods until they were simply myths. Unable to survive without the love, admiration, and worship they thrived on, the aliens departed Earth to eventually settle on Pollux IV. (TOS: "Who Mourns for Adonais?")

Despite their absence, Greek mythology remained a cornerstone of Humanity since many astrographic names, such as those of planets, trace their origins to Greek mythology.

Roman Gods based on the Greek are mentioned in TOS: "Bread and Circuses". It is not explained in the episode if these modern Roman Gods are intended to be the same ones mentioned in "Who Mourns for Adonais?".